/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.log4j.config;

import java.beans.*;
import java.lang.reflect.*;
import org.apache.log4j.Priority;
import org.apache.log4j.helpers.LogLog;

/**
 * Used for inferring configuration information for a log4j's component.
 * 
 * @author Anders Kristensen
 */
public class PropertyGetter {
	protected static final Object[] NULL_ARG = new Object[]{};
	protected Object obj;
	protected PropertyDescriptor[] props;

	public interface PropertyCallback {
		void foundProperty(Object obj, String prefix, String name, Object value);
	}

	/**
	 * Create a new PropertyGetter for the specified Object. This is done in
	 * prepartion for invoking
	 * {@link #getProperties(PropertyGetter.PropertyCallback, String)} one or
	 * more times.
	 * 
	 * @param obj
	 *            the object for which to set properties
	 */
	public PropertyGetter(Object obj) throws IntrospectionException {
		BeanInfo bi = Introspector.getBeanInfo(obj.getClass());
		props = bi.getPropertyDescriptors();
		this.obj = obj;
	}

	public static void getProperties(Object obj, PropertyCallback callback,
			String prefix) {
		try {
			new PropertyGetter(obj).getProperties(callback, prefix);
		} catch (IntrospectionException ex) {
			LogLog.error("Failed to introspect object " + obj, ex);
		}
	}

	public void getProperties(PropertyCallback callback, String prefix) {
		for (int i = 0; i < props.length; i++) {
			Method getter = props[i].getReadMethod();
			if (getter == null)
				continue;
			if (!isHandledType(getter.getReturnType())) {
				// System.err.println("Ignoring " + props[i].getName() +" " +
				// getter.getReturnType());
				continue;
			}
			String name = props[i].getName();
			try {
				Object result = getter.invoke(obj, NULL_ARG);
				// System.err.println("PROP " + name +": " + result);
				if (result != null) {
					callback.foundProperty(obj, prefix, name, result);
				}
			} catch (Exception ex) {
				LogLog.warn("Failed to get value of property " + name);
			}
		}
	}

	protected boolean isHandledType(Class type) {
		return String.class.isAssignableFrom(type)
				|| Integer.TYPE.isAssignableFrom(type)
				|| Long.TYPE.isAssignableFrom(type)
				|| Boolean.TYPE.isAssignableFrom(type)
				|| Priority.class.isAssignableFrom(type);
	}
}
